Radio access management system

ABSTRACT

A radio access management system includes a radio access network including a number of base stations; a backhaul network to which the base stations are connected via backhaul links, and a backhaul resource controller configured to acquire information about both the load of the radio access network and of the backhaul network and to at least one of suggest or enforce handovers of user terminals connected to the base stations based on the acquired load information. The backhaul resource controller is connected via a first interface to a local cluster of base stations, wherein the local cluster of base stations includes at least a subset of the base stations.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/442,733, which is a continuation of U.S. patent application Ser. No.14/783,469, now U.S. Pat. No. 9,717,029, both of which are incorporatedby reference herein. U.S. patent application Ser. No. 15/442,733 wasfiled on Feb. 27, 2017 and was published on Jun. 15, 2017 as U.S. PatentApplication Publication No. 2017/0171789. U.S. patent application Ser.No. 14/783,469 was filed on Oct. 9, 2015 and is a U.S. National StageApplication under 35 U.S.C. § 371 of International Application No.PCT/EP2013/057670 (which was filed on Apr. 12, 2013 and published inEnglish on Oct. 16, 2014 as WO2014/166544 A1).

FIELD

The present invention relates to a radio access management system and toa method for performing radio access management involving a radio accessnetwork including a number of base stations and a backhaul network towhich said base stations are connected via backhaul links. Further, thepresent invention relates to a backhaul resource controller forsupporting radio access management in a radio access network thatincludes a number of base stations that are connected to a backhaulnetwork via backhaul links.

BACKGROUND

The last decades brought an exponential increase in mobile trafficvolume. This will continue and a 1000-fold increase by 2020 has beenforecasted. Small-cells are capable of enabling new services, increasingenergy-efficiency, and reducing the costs of handling explosive datagrowth.

Due to strong inter-cell interference, small-cell deployments willrequire a higher degree of coordination than currently deployed systems.Small-cells may be deployed where it is difficult or too expensive todeploy fixed broadband access, optical fiber or line-of-sight (LOS)based microwave solutions for backhaul. The Broadband Forum (seehttp://www.broadband-forum.org for reference) reported that 30% of amobile operator's OPEX today is spent for backhaul networks. Recently,wireless backhaul has received more attention due to its higherdeployment flexibility and lower costs. The report “Wireless Backhaul:The Network Behind LTE, WiMAX, and 3G”, In Stat, October 2010 shows thatthe expenditures for wireless backhaul will increase by 41% from 2009 to2014. Hence, small-cell deployments must be connected by heterogeneousbackhaul technologies that consist of fiber, microwave solutions, aswell as other forms of wireless backhaul (for reference see NGMNAlliance (Next Generation Mobile Networks), “Next Generation MobileNetworks Optimised Backhaul Requirements,” NGMN Alliance, August 2008).

So far, most radio access designs (including 3GPP architecture) considerthe backhaul network to be sufficiently dimensioned (over-provisioned).While this is already challenging in today's backhaul networks, it mightbe even less true as we move towards small cells and more coordinatedoperation. Therefore, the backhaul must be considered as a limitedresource when operating the radio access network. However, the 3GPP LTEmobile network architecture provides no means to take into account theunderlying physical transport network and functional split of thephysical implementation.

If a backhaul link is congested, this may be solvable in many cases bymeans of re-routing traffic over alternative paths if such exist.However, the closer to the base station, the less path diversity of thebackhaul topology is typically available. Given two or more small cellbase stations (or a combination of small cell and macro base stations)with overlapping coverage areas, the only remedy to relieve congestedbackhaul links might therefore be to enforce mobility of individual userterminals from one cell to another so that traffic destined for thoseterminals can be routed via a different and less congested part of thebackhaul network.

In R. Ferrus, J. Olmos, and H. Galeana: “Evaluation of a cell selectionframework for radio access networks considering backhaul resourcelimitations,” IEEE International Symposium on Personal, Indoor andMobile Radio Communications, Athens (Greece), September 2007, theauthors discuss a cell selection framework for radio access networkswhich considers backhaul resource limitations. By means of an analyticalframework, they show the benefits of taking into account backhaullimitations for the selection of radio access nodes. In fact, thedocument discloses the use of a very general formulation through amulti-dimensional Markov chain to show that treating allbackhaul-resources as one pool of resources (trunk pool) will increasethe overall capacity (trunking gain) that may be assigned to differentcells.

WO 2009/067297 A1 discloses a cellular communication system thatperforms serving cell management in response to the backhaul loading ofthe base stations of the system. To this end, the base stations areequipped with a buffer including a plurality of sub-buffers forbuffering backhaul data and with means for determining backhaul loadingcongestion. The system considers the backhaul load from a base stationperspective, which renders the system rather inefficient and inflexible.

SUMMARY

In an embodiment, the present invention provides a radio accessmanagement system. The radio access management system includes a radioaccess network including a number of base stations; a backhaul networkto which the base stations are connected via backhaul links, and abackhaul resource controller configured to acquire information aboutboth the load of the radio access network and of the backhaul networkand to at least one of suggest or enforce handovers of user terminalsconnected to the base stations based on the acquired load information.The backhaul resource controller is connected via a first interface to alocal cluster of base stations, wherein the local cluster of basestations includes at least a subset of the base stations.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be described in even greater detail belowbased on the exemplary figures. The invention is not limited to theexemplary embodiments. All features described and/or illustrated hereincan be used alone or combined in different combinations in embodimentsof the invention. The features and advantages of various embodiments ofthe present invention will become apparent by reading the followingdetailed description with reference to the attached drawings whichillustrate the following:

FIG. 1 is a schematic view of a radio access management system inaccordance with an embodiment of the present invention, and

FIG. 2 is a flow chart showing message exchange flow in a method forperforming radio access management in accordance with an embodiment ofthe present invention.

DETAILED DESCRIPTION

In an embodiment, the present invention provides improvements andfurther developments to a radio access management system and a methodfor performing radio access management as well as to a backhaul resourcecontroller for supporting radio access management in a radio accessnetwork in such a way that a more efficient and coordinated radio accessand backhaul resource usage is enabled.

In an embodiment, a system is provided that includes a backhaul resourcecontroller which is configured to acquire information about both theload of said radio access network and of said backhaul network and tosuggest and/or to enforce handovers of user terminals connected to saidbase stations based on said acquired load information.

In an embodiment, method is provided that involves a backhaul resourcecontroller that acquires information about both the load of said radioaccess network and of said backhaul network and that suggests and/orenforces handovers of user terminals connected to said base stationsbased on said acquired load information.

In an embodiment, a backhaul resource controller for supporting radioaccess management in a radio access network is provided, wherein thebackhaul resource controller comprises a first interface for acquiringinformation about the load of said radio access network, a secondinterface for acquiring information about the load of said backhaulnetwork, and an evaluator for evaluating said acquired load informationand for suggesting and/or enforcing handovers of user terminalsconnected to said base stations based on said acquired load information.

According to the invention it has been recognized that a highlyefficient and coordinated backhaul resource usage is achieved bydeployment of a network entity that collects information, in particularload information, both from the radio access side as well as from thebackhaul side. Such load information acquisition results in the abilityto optimize jointly the backhaul and access network operation. Inparticular, according to the present invention the backhaul resourcecontroller can prepare handover decisions taking into consideration theoverall load situation. In this regard the backhaul resource controllercan be regarded as a global entity overseeing the backhaul as a wholeperforming backhaul-information based radio access management.Consequently, the backhaul resource controller can, e.g., identifybottlenecks somewhere up in the backhaul which cannot be discovered bythe base stations themselves.

With respect to the handover of user terminals from a source cell to atarget cell it may be provided that the backhaul resource controllerprovides to the base stations under its control acausal informationabout backhaul and radio access network load before handover, while thehandover is then performed by the base stations based on the informationreceived from the backhaul resource controller. Alternatively, thebackhaul resource controller may initiate handovers independently basedon monitored backhaul traffic.

For instance, based on the joint information from radio access andbackhaul network, the backhaul resource controller could decide todynamically grant more capacity to particular base stations if they needit. So instead of base stations seeing the load and enforcing handoversin case their granted capacity is approaching critical thresholds, thebase stations, according to embodiments of the present invention, couldjust communicate with the backhaul resource controller to negotiatewhether more resources can be granted. Alternatively, the backhaulresource controller could grant the resources proactively. This allowsmuch better coordination and much better resource usage. Consequently,the present invention is highly beneficial in small cell networks wherebackhaul is of particular importance. Furthermore, it enables theintegration of backhaul-capacity-limited base stations into existingradio access networks.

The policies and objectives to be pursued by the backhaul resourcecontroller may be preset or dynamically adapted, for instance by theoperator of the radio access network. The present invention particularlyaddresses the problem of mobility, network-wide load balancing andenergy efficiency controlled by a central entity. From a userperspective, improved load balancing will significantly improve the userexperience. From an operator perspective, using non-ideal backhaulinstead of expensive ideal backhaul results in considerable reductionsof CAPEX and OPEX for the mobile network.

According to a preferred embodiment the backhaul resource controller maybe connected via a first interface to at least a subset of the number ofbase stations, in particular to a local cluster of base stations.Advantageously, the first interface is implemented as a logicalinterface towards connected base stations, i.e. the backhaul resourcecontroller will appear as logical basestation (as described in thestandardization document 3GPP TS 36.300 “Technical Specification GroupRadio Access Network; Evolved Universal Terrestrial Radio Access(E-UTRA) and Evolved Universal Terrestrial Radio Access Network(E-UTRAN); Overall description, Release 11”) towards the involved basestations. For instance, in 3GPP LTE the first interface may beimplemented as the X2 interface, which will allow the backhaul resourcecontroller to reuse already existing X2 information elements ascoordination messages. Therefore, the backhaul resource controller doesnot need to be revealed towards the connected base stations. It is notedthat the term “coordination messages” as used herein in connection witha 3GPP LTE architecture refers to messages exchanged between thebackhaul resource control and the assigned cluster of base stations aswell as the connecting backhaul network.

In order to enable the backhaul resource controller to acquire loadinformation from the backhaul network, it may be provided that thebackhaul resource controller is connected to the backhaul network via asecond interface. Preferably, the first and the second interfaces arecoordinated in such a way that, when the first interface connects thebackhaul resource controller to a local base station cluster, the secondinterface connects the backhaul resource controller to the localbackhaul infrastructure which delivers the data to that base stationcluster.

According to a preferred embodiment the backhaul resource controller maybe configured to assign a utility value to each of the base stationsbeing under its control, wherein the utility value represents theacceptability or desirability of a particular of the base stations toaccept further user terminals (for new connection requests or as part ofhandovers). The backhaul resource controller may perform feeding in of autility value as a pre-step upon which the base station can then baseits handover decisions, thereby resolving congestion on the backhaulnetwork and increasing the actual throughput on the radio accessnetwork.

Generally, the utility value will be based on backhaul-motivatedcriteria such a backhaul load (on links directly or indirectly connectedto the given base station) or energy saving goals, etc. According to apreferred embodiment the utility value assigned to a base station mayrelate to the relative load of backhaul links connecting to thatbase-station, as well as to the relative load of backhaul linksconnecting to adjacent base-stations. Furthermore, the utility valueassigned to a base station may be determined by taking intoconsideration the absolute available load on backhaul links. Based onthe provided utility value, various implications for the radio accessnetwork can be envisioned, among them, for instance,

-   -   Scaling factor for measurements which are applied to measurement        reports of user terminals in order to change the handover        behavior,    -   Changing handover parameters in order to reduce the amount of        UEs that may connect to a cell while adjacent cells may accept        more UEs, and/or    -   A lower/upper bound for user traffic flows that may be        accepted/rejected at a base station.

As part of the normal handover procedure, the base stations may takeinto consideration their assigned utility value in order to makebackhaul-information based handover decisions. This is particularly thecase, if the utility value was an existing standardized 3GPP protocolfield (such as the 51 Transport Network Load Indicator for LTE).

According to a preferred embodiment the backhaul resource controller maybe configured to use a coordination message which requests user terminalspecific load information from a source cell. In this case, the basestation of the source cell would send for all or a group of connecteduser terminals the current load information. The backhaul resourcecontroller comprises an evaluator which then matches this loadinformation with the available backhaul capacity as well as theavailable capacity in potential target cells. For instance, the basestation of a source cell could provide a list of user terminals sortedaccording to the user terminals' load. In this case, the backhaulresource controller could initiate a handover for each user terminal oneafter the other. The process could be stopped as soon as the backhaulresource controller discovers that a particular objective, e.g.specified by the network operator, is achieved. The objective may relateto, but not limited to, achieving load balancing on the radio accesslayer or on the backhaul, resolving contention, or realizingenergy-saving on the backhaul.

According to another preferred embodiment the backhaul resourcecontroller may be configured to acquire the load information on theradio access layer using the RESOURCE STATUS UPDATE message,particularly Hardware Load Indicator, Radio Resource Status, andComposite Available Capacity, as specified in the standardizationdocument 3GPP TS 36.423 V11.4.0, “Technical Specification Group RadioAccess Network; Evolved Universal Terrestrial Radio Access Network(E-UTRAN); X2 application protocol (X2AP), Release 11” (see inparticular section 9.1.2.14). Additionally or alternatively the backhaulresource controller may acquire the load information on the radio accesslayer using the LOAD INFORMATION message, in particular interferenceindication information elements (see in particular section 9.1.2.1).

With regards to an efficient information management, the backhaulresource controller may use a coordination message to inform a basestation about available resources on a target cell which are matchedwith available backhaul resources such that reported available resourceson the target cell will not exceed available backhaul resources. In thiscase, the base station of a source cell may decide which user terminalscan be handed over to the target cell based on the available resourcesas well as available measurement reports from the user terminals. Asalready indicated earlier, the process of deciding on (and enforcing)handovers of user terminals based on reported matching availableresources may also be performed directly by the backhaul resourcecontroller itself.

Advantageously, the backhaul resource controller may further monitor theexchanged backhaul data in order to identify flows that may be reroutedfrom a source to a target cell based on the available load informationfrom the individual base stations. In this case, the handover may besuggested to the source cell using a coordination message.

According to a preferred embodiment the backhaul resource controller mayuse available measurement drive test (MDT) information elements (asspecified in the standardization document 3GPP TS 37.320 “TechnicalSpecification Group Radio Access Network; Evolved Universal TerrestrialRadio Access (E-UTRA) and Evolved Universal Terrestrial Radio AccessNetwork (E-UTRAN); Radio measurement collection for Minimization ofDrive Tests (MDT); Overall description, Release 11”) in order to decideon the handover of a particular user terminal. As a result, by thebackhaul resource controller exploiting MDT information, backhaulresource usage and user terminal mobility can be further optimized.Among others, the backhaul resource controller may reuse the availablereference signal receive power (RSRP) or reference signal receivequality (RSRQ) in order to decide whether a user terminal or a group ofuser terminals may be handed over to another cell.

With respect to a high degree of flexibility and adaptability, it may beprovided that the backhaul resource controller dynamically re-arrangesthe controlled subset of base stations. To this end the backhaulresource controller may use the ENB CONFIGURATION UPDATE message, asspecified in the standardization document 3GPP TS 36.423 V11.4.0,“Technical Specification Group Radio Access Network; Evolved UniversalTerrestrial Radio Access Network (E-UTRAN); X2 application protocol(X2AP), Release 11” (see in particular section 9.1.2.8).

If the backhaul resource controller encounters that within a certaincluster of base stations rather the radio access network capacity thanthe backhaul network capacity is the limited factor, it may be providedthat then the backhaul resource controller re-activates base stations.This is of particular interest for an energy-efficient operation of thenetwork where base stations are turned off for energy-saving reasons ifthey are not used. For the re-activation of shut down base stationsbased on backhaul-load information the backhaul resource controller mayuse the CELL ACTIVATION REQUEST, as specified in the standardizationdocument 3GPP TS 36.423 V11.4.0, “Technical Specification Group RadioAccess Network; Evolved Universal Terrestrial Radio Access Network(E-UTRAN); X2 application protocol (X2AP), Release 11” (see inparticular section 9.1.2.20).

According to one embodiment the backhaul resource controller may beimplemented as a dedicated entity that is specifically provided for thepurpose of making handover decisions on the basis of load informationacquired both from the radio access network and from the backhaulnetwork. According to another embodiment it may be provided that thecoordination of backhaul and radio resources is implemented as part ofthe Element Manager (as described in document Self Organizing Network“NEC's proposals for next-generation radio network management”, Whitepaper, NEC Corporation, February 2009, see in particular FIG. 2) whichcontrols a set of base stations or using a direct connection between thebackhaul resource controller and the Element Manager. In this case,existing coordination messages between the Element Manager and thenetwork may be reused or extended to influence the radio resourceallocation. Alternatively, the coordination of backhaul and radioresources can also be implemented as part of the Network Manager (asalso described in the above document) or using a direct connectionbetween the backhaul resource controller and the Network Manager. Inthis case, existing coordination messages between the Network Managerand the network may be reused or extended to influence the radioresource allocation.

FIG. 1 schematically illustrates a radio access management system inaccordance with an embodiment of the present invention. The systemcomprises a radio access network, generally denoted 1, and a backhaulnetwork, generally denoted 2. The radio access network 1 includes anumber of base stations 3 which provide connectivity to user terminals4. In FIG. 1, for the sake of simplicity, only one or two user terminals4 are depicted per base station 3. However, as will be appreciated bythose skilled in the art, in real scenarios each base station 3typically serves a multitude of user terminals 4.

In accordance with the present invention the radio access managementsystem illustrated in FIG. 1 comprises a backhaul resource control (BRC)5 which is connected via a first interface I₁ to a local cluster 6 ofbase stations 3. In the illustrated embodiment, the cluster 6 of basestations 3 being under control of BRC 5 includes a total number of fivebase stations 3. However, as will be appreciated by those skilled in theart, the number of base stations 3 may be different. In particular, thecluster 6 can be dynamically modified in order to adapt the system tothe current situation, e.g. the current load distribution. Via a secondinterface I₂ BRC 5 is connected to the backhaul network 2, i.e. to thelocal backhaul infrastructure which delivers the data to the basestation cluster 6. As illustrated in FIG. 1, the backhaul infrastructuretypically includes various backhaul aggregation hubs that aggregatebackhaul traffic from multiple base stations 3 or other backhaul nodes.

It is assumed that the backhaul link capacities C₁-C₅ limit the maximumthroughput on each backhaul link. It is noted that the solid linesindicate wired connections, such as optical fibre, whereas the dashedlines indicate wireless links, such as microwave or 60 GHz, forinstance. FIG. 1 illustrates a scenario in which the sum of C₁+C₂+C₃ islimited by C_(A1), while the sum of C₄+C₅ is limited by C_(A2).

In accordance with embodiments of the present invention the BRC 5acquires load information from the local base station cluster 6 viainterface I₁ and from the connecting backhaul network 2 via interface I₂in order to enforce (or at least suggest) handovers between source andtarget cells to resolve congestion on the backhaul network 2 andincrease the actual throughput on the radio access network 1. Forinstance, in the scenario of FIG. 1 the load information regarding thecurrent load on the radio access layer acquired by BRC 5 may reveal thatthe backhaul capacity of Cal is fully saturated. In this case, the BRC 5may suggest that the user terminal UE₁, which is connected to the basestation connected through C₃, could be handed over to the base stationconnected through C₄ in order to free up capacity on C₃ and thereforeincrease the capacity for the remaining user terminals connected throughCAL In order to perform such a “backhaul motivated handover”, the BRC 5uses information from both the radio access network 1 and the backhaulnetwork 2, which is described hereinafter in more detail.

As a pre-step, the BRC 5 could feed a “utility value” to each of thebase stations 3 of the cluster 6, where the utility value represents thedesirability of a particular base station 3 to accept further userterminals (for new connection requests or as part of handovers). Theutility value is based on backhaul-motivated criteria such as backhaulload (on links directly or indirectly connected to the given basestation 3) or energy saving goals. Specifically, the utility valueassigned to a particular base station 3 of a base station cluster 6 mayrelate to the relative load of backhaul links to that particularbase-station 3, as well as to the relative load of backhaul links toadjacent base-stations 3. Moreover, the utility value may relate to theabsolute available load on backhaul links. As part of the normalhandover procedure, base stations 3 could then take the utility valueinto consideration in order to make handover decisions with backhaulconditions in mind.

In FIG. 2, the radio access management method and system described aboveis illustrated as a flow chart. As can be seen, the BRC 5 updates itsload information both with respect to the backhaul network 2 and withrespect to the radio access network 1. As regards the radio accessnetwork 1 load information, the BRC 5 performs update measurementstowards the base stations 3 belonging to the base station cluster 6under its control. These update measurements rely on the results ofupdate measurements performed by the base stations 3 towards connecteduser terminals 4. For instance, the BRC 5 may use a coordination messagewhich requests user terminal specific load information from a sourcecell. In this case, the source cell, i.e. the respective base station,sends for all or a group of connected user terminals 4 the current loadinformation. This load information may then be matched with theavailable backhaul capacity as well as the available capacity inpotential target cells.

On the basis of the acquired load information, the BRC 5 determinesappropriate utility values for the base stations 3 and transmitsrespective update messages to the base stations 3. In addition the BRC5, taking into consideration the updated utility values, prepareshandover decisions and transmits respective proposals/recommendations tothe base stations 3. According to one embodiment the BRC 5 provides alist of user terminals 4 sorted according to the user terminals' 4 load.In this case, the BRC could initiate/propose a handover for each userterminal 4 one after the other until the preset objectives (e.g.resolving contention, energy-saving on the backhaul, etc.) are achieved.Based on the handover proposals received from the BRC 5, the basestations 3 may perform corresponding cell re-reassignments and givefeedback to the BRC 5.

While the invention has been illustrated and described in detail in thedrawings and foregoing description, such illustration and descriptionare to be considered illustrative or exemplary and not restrictive. Itwill be understood that changes and modifications may be made by thoseof ordinary skill within the scope of the following claims. Inparticular, the present invention covers further embodiments with anycombination of features from different embodiments described above andbelow.

The terms used in the claims should be construed to have the broadestreasonable interpretation consistent with the foregoing description. Forexample, the use of the article “a” or “the” in introducing an elementshould not be interpreted as being exclusive of a plurality of elements.Likewise, the recitation of “or” should be interpreted as beinginclusive, such that the recitation of “A or B” is not exclusive of “Aand B,” unless it is clear from the context or the foregoing descriptionthat only one of A and B is intended. Further, the recitation of “atleast one of A, B and C” should be interpreted as one or more of a groupof elements consisting of A, B and C, and should not be interpreted asrequiring at least one of each of the listed elements A, B and C,regardless of whether A, B and C are related as categories or otherwise.Moreover, the recitation of “A, B and/or C” or “at least one of A, B orC” should be interpreted as including any singular entity from thelisted elements, e.g., A, any subset from the listed elements, e.g., Aand B, or the entire list of elements A, B and C.

What is claimed is:
 1. A radio access management system, comprising: aradio access network including a number of base stations; a backhaulnetwork to which the base stations are connected via backhaul links, anda backhaul resource controller configured to acquire information aboutboth the load of the radio access network and of the backhaul networkand to at least one of suggest or enforce handovers of user terminalsconnected to the base stations based on the acquired load information,wherein the backhaul resource controller is connected via a firstinterface to a local cluster of base stations, wherein the local clusterof base stations includes at least a subset of the base stations, andwherein the backhaul resource controller is configured to dynamicallyre-arrange the local cluster of base stations.
 2. The radio accessmanagement system according to claim 1, wherein the backhaul resourcecontroller is configured to issue an eNB configuration update message inorder to dynamically re-arranged the local cluster of base stations. 3.The radio access management system according to claim 1, wherein thefirst interface is implemented as a logical interface towards the localcluster of base stations.
 4. The radio access management systemaccording to claim 1, wherein the backhaul resource controller isconnected via a second interface to the backhaul network.
 5. The radioaccess management system according to claim 1, wherein the backhaulresource controller is configured to assign, to each of the basestations a utility value which represents the acceptability of that basestation to which it is assigned to serve further user terminals.
 6. Theradio access management system according to claim 5, wherein the utilityvalue assigned to a base station relates to a relative load of backhaullinks connecting to that base-station to which it assigned as well as tothe relative load of backhaul links connecting to adjacentbase-stations.
 7. A radio access management system, comprising: a radioaccess network including a number of base stations; a backhaul networkto which the base stations are connected via backhaul links, and abackhaul resource controller configured to acquire information aboutboth the load of the radio access network and of the backhaul networkand to at least one of suggest or enforce handovers of user terminalsconnected to the base stations based on the acquired load information,wherein the backhaul resource controller is connected via a firstinterface to a local cluster of base stations, wherein the local clusterof base stations includes at least a subset of the base stations, andwherein the backhaul resource controller is configured to re-activatedeactivated base stations when the radio access network within the localcluster of base stations has limited resources.
 8. The radio accessmanagement system according to claim 7, wherein the deactivated basestations were deactivated in response to not being in use.
 9. The radioaccess management system according to claim 7, the backhaul resourcecontroller is configured to issue a cell activation request message tore-activate the deactivated base stations.
 10. The radio accessmanagement system according to claim 7, wherein the backhaul resourcecontroller is configured to determine that the radio access networkwithin the local cluster of base stations has limited resources, andwherein the backhaul resource controller is configured to re-activatedeactivated base stations in response to said determination.
 11. Theradio access management system according to claim 1, wherein thebackhaul resource controller is configured to assign, to each of thebase stations a utility value which represents the acceptability of thatbase station to which it is assigned to serve further user terminals.12. The radio access management system according to claim 11, whereinthe utility value assigned to a base station relates to an absoluteavailable load on backhaul links.
 13. The radio access management systemaccording to claim 11, wherein the utility value assigned to a basestation relates to at least one of a lower or an upper bound for usertraffic flows that is at least one of accepted or rejected at that basestation to which it is assigned.
 14. The radio access management systemaccording to claim 11, wherein the base stations take into considerationtheir assigned utility value in order to make handover decisions. 15.The radio access management system according to claim 1, wherein thebackhaul resource controller is configured to use a coordination messagewhich requests user terminal specific load information from a sourcecell.